|  | 2.2 |
Full-Duplex Transmitting, Fast Ethernet Standard and LAN Segmentation
| 2.2.3 | LAN segmentation with bridges
Ethernet LANs that use a bridge to segment the LAN provide more bandwidth per user because there are fewer users on each segment. In contrast, LANs that do not use bridges for segmentation provide less bandwidth per user because there are more users on a nonsegmented LAN. Bridges "learn" a network's segmentation by building address tables that contain the address of each network device and which segment to use to reach that device. Bridges are Layer 2 devices that forward data frames according to the frames' Media Access Control (MAC) addresses. In addition, bridges are transparent to the other devices on the network. Bridges increase the latency in a network by 10%-30%. This latency is due to the decision making required of the bridge or bridges in transmitting data. A bridge is considered a store-and-forward device because it must examine the destination address field and calculate the CRC in the frame check sequence field, before forwarding the frame to all ports. If the Destination port is busy, the bridge can temporarily store the frame until the port is available. The time it takes to perform these tasks slows the network transmissions causing increased latency.
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| Bridging